I've written down some of these questions before, but for kicks I thought I'd post them here. They range from the deep to the absurd.
Now keep in mind that eternal youth does not mean invulnerability. It just means you won't age. You could still be hit by a bus, or die of cancer. Let's also start with the posit that all people world-wide are given the secret simultaneously and that aging occurs normally until you reach 18. Anyone already past that age has the choice to stop aging or continue aging normally.
Well, anyway, there they are. Feel free to add more or comment on these.